Orthokeratology

Encyclopedia : O : OR : ORT : Orthokeratology

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Orthokeratology (Ortho-K) is the use of rigid gas permeable contact lenses, normally worn only at night, to improve vision through the reshaping of the cornea. This method can be used as an alternative to eyeglasses, refractive surgery, or for those desiring to not wear contact lenses during the day.

Contents

1 History
2 Mechanism
3 Indications
4 Types of lenses
5 Costs
6 External links

History

The idea of correcting vision by reshaping the cornea has been around for a while. Doctors discovered the reshaping phemomena of glass lenses as early as the 40's.

George Jessen created what was probably the first orthokeratology design in the 60's made from PMMA material, which he marketed as "Orthofocus". These early designs had generally unpredictable results, leading to the belief that applied orthokeratology was more art or luck than science.

Not until new measuring instruments and computers were available was it possible to apply the theory to create designs with repeatable results.

Many groups and individuals claim to have been the first to develop modern orthokeratology solutions. But Dr. Richard Wlodyga, in particular, is generally credited with developing the first reverse zone lens design in the 80's.

A significant milestone for the American market occurred in June 2002 when the FDA granted approval for overnight wear of a type of corneal reshaping called "Corneal Refractive Therapy (CRT)". This forms the basis of the "Paragon CRT" product backed by Paragon Vision Sciences Inc.

In 2004 the FDA approved a number of ortho-k designs for overnight wear, including designs from Contex ("Contex OK-E") and Euclid Systems ("Emerald"). 2005 saw additional FDA approvals, as manufacturers raced to bring orthokeratology to American consumers. However, nightwear ortho-k solutions were available to consumers in many countries outside the US much earlier as a result of different regulatory controls and bodies.

In 2005, Bausch & Lomb introduced the "Vision Shaping Treatment" (VST) program to collectively market a number of ortho-k products.

Mechanism

It is presumed that the lenses used in orthokeratology reshape the cornea by moving the epithelial cells that cover the surface of the cornea. Some studies indicate that the epithelial cells are compressed in some areas as well as relocated.

Indications

In the United Kingdom, the treatment is currently offered for corrections from +3.00 to -6.00D, with possible treatment upto -8.50D. Some patients may not be suitable for treatment. The US FDA approvals are for procedures up to -6D. Some patients with higher degrees of myopia are successfully treated by specialty practitioners with "off-label" uses of these same lenses.

Types of lenses

Orthokeratology lenses are made by several companies, using one of two FDA approved technologies. All use special gas permeable lenses to reshape the cornea. The lens material is important for maintaining eye-health during the treatment.

Paragon Vision Sciences manufactures a lens trademarked the CRT (Corneal Refractive Therapy) and marketed as "Accelerated Orthokeratology" (AOK). Bausch & Lomb's "Vision Shaping Treatment" offers the choice of four approved designs that may only be fit by certified practitioners. The four designs in the VST portfolio include (alphabetically) "BE Retainer" backed by BE Enterprises Inc, "Contex OK-E System" backed by Contex Inc., "DreamLens" backed by Dreimlens Inc, and "Emerald" backed by Euclid Systems Corp.

Only a few other brands of ortho-k lenses have been approved by the FDA for overnight wear. Currently no other studies are underway for any other lens designs.

Costs

In the United States, the initial cost of orthokeratology for both eyes typically varies from $800 to $1,500, however, there are generally additional fitting fees and lens costs from year-to-year. In the United Kingdom, costs are typically from £600 upwards, this would include aftercare for a year. The procedure was being promoted in September 2005 at £100 for an initial fitting and £40 per month for aftercare.

External links

[The Ortho-K Network] (Ortho-K information)
[The Orthokeratology Academy of America] (Professional Organization) (NOTE: Website is 100% flash and even their claim of a non-flash site is also 100% flash.)
[The British Orthokeratology Society] (Professional Organization)
[Paragon CRT] (CRT lenses)
[Bausch & Lomb] (B&L VST Program)
[BE Enterprises] (BE Retainer design)
[Contex Inc.] (Contex OK E-System design)
[DreamLens] (DreamLens design)
[Euclid Systems] (Emerald design)
[What Is Orthokeratology] (About.com article)
[VisionSimulations.com | Images and vision simulators of various diseases and conditions of the eye]
[Personal account of othokeratology treatment] (Sydney-based blogger)

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